/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.time;

import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

import org.apache.commons.io.IOUtils;

/**
 * The TimetSimpleServer class is a simple TCP implementation of a server for the Time Protocol described in RFC 868.
 * <p>
 * Listens for TCP socket connections on the time protocol port and writes the local time to socket outputStream as 32-bit integer of seconds since midnight on
 * 1 January 1900 GMT. See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A> for details.
 * <p>
 * Note this is for <strong>debugging purposes only</strong> and not meant to be run as a realiable time service.
 */
public class TimeTestSimpleServer implements Runnable {

    /**
     * baseline time 1900-01-01T00:00:00 UTC
     */
    public static final long SECONDS_1900_TO_1970 = 2208988800L;

    /** The default time port. It is set to 37 according to RFC 868. */
    public static final int DEFAULT_PORT = 37;

    public static void main(final String[] args) {
        final TimeTestSimpleServer server = new TimeTestSimpleServer();
        try {
            server.start();
        } catch (final IOException e) {
            // ignored
        }
    }

    private ServerSocket server;
    private final int port;

    private boolean running;

    public TimeTestSimpleServer() {
        port = DEFAULT_PORT;
    }

    public TimeTestSimpleServer(final int port) {
        this.port = port;
    }

    public void connect() throws IOException {
        if (server == null) {
            server = new ServerSocket(port);
        }
    }

    public int getPort() {
        return server == null ? port : server.getLocalPort();
    }

    public boolean isRunning() {
        return running;
    }

    @Override
    public void run() {
        Socket socket = null;
        while (running) {
            try {
                socket = server.accept();
                final DataOutputStream os = new DataOutputStream(socket.getOutputStream());
                // add 500 ms to round off to nearest second
                final int time = (int) ((System.currentTimeMillis() + 500) / 1000 + SECONDS_1900_TO_1970);
                os.writeInt(time);
                os.flush();
            } catch (final IOException e) {
                // ignored
            } finally {
                IOUtils.closeQuietly(socket, e -> System.err.println("close socket error: " + e));
            }
        }
    }

    /*
     * Start time service and provide time to client connections.
     */
    public void start() throws IOException {
        if (server == null) {
            connect();
        }
        if (!running) {
            running = true;
            new Thread(this).start();
        }
    }

    /*
     * Close server socket.
     */
    public void stop() {
        running = false;
        if (server != null) {
            IOUtils.closeQuietly(server, e -> System.err.println("close socket error: " + e));
            server = null;
        }
    }

}
